What you don't know can hurt you when the subject is heart disease. And according to a new report from the Cleveland Clinic, there's a fair amount Americans don't know.

A phone survey of more than 1,000 U.S. adults revealed that almost three-quarters don't fear that they will die from heart disease, even though it is the leading cause of death in the United States and most respondents said they know someone with the condition.

The survey revealed there's also some confusion about heart-disease symptoms. For example, though most people know salt isn't good for the heart, they don't know which foods are responsible for most of the sodium in the American diet.

There are misconceptions about how much cigarettes can hurt the heart and exercise can help it. The researchers say 20 percent of heart-disease deaths are related to smoking, but about one-third of survey respondents guessed it was less than that. Similarly, about half of respondents underestimated how much regular exercise can cut a person's risk of dying from heart disease. The researchers say it could cut the risk 30 percent to 50 percent.

The good news is that most people surveyed said they are willing to change something about their lifestyle if it will decrease their risk of heart disease. Sixty-seven percent said they would exercise more, and slightly fewer, 63 percent, said they'd modify their diets.